Tubular heat exchangers



July 12, 1966 J. w. w. DAWSON TUBULAR HEAT EXCHANGERS 2 Sheets-Sheet 1 Filed July 28, 1964 July 12, 1966 J. w. w. DAWSON TUBULAR HEAT EXCHANGERS 2 Sheets-Sheet 2 Filed July 28, 1964 United States Patent O 3,260,307 TUBULAR HEAT EXCHANGERS James W. W. Dawson, Newcastle upon Tyne, England,

assignor to C. A. Parsons & Company Limited, Newcastle upon Tyne, England Filed July 28, 1964, Ser. No. 385,571 Claims priority, application Great Britain, Aug. 2, 1963, 30,697/ 63 3 Claims. (Cl. 165-158) This invention relates to tubular heat exchangers particularly, though not exclusively, high pressure boiler feedwater heaters for steam turbine plant.

In high pressure boiler tubular feedwater heaters for steamturbine plant it is common practice to circulate the feedwater through the tubes and to circulate steam from a turbine stage over the tubes. The feedwater enters and leaves the tubes via headers at each end of the tubes. In one form of heater the tubes are arranged in U- shaped banks andthe inlet and outlet ends of the tubes are joined to a common fiat tube plate. The headers for the inlet: and'outlet of the feedwater are arranged sidelby sideon the end face of-the tube plate remote from the tubes and are joined to the tube plate. The headers may be formed by welding a housing in the form of a solid forging to the tube plate and dividing the space within the housing into two separate headers by means of a dividing wall.

If a boiler feed pump for returning feedwater to a boiler is located on the inlet side of such a heater the feedwater pressure in the heater is in excess of the boiler steam pressure and the tube plate has thus to withstand very high forces due to the large pressure difference between the feedwater pressure on one side thereof and the steam pressure on the other side thereof. The tube plate to withstand such forces in modern steam turbine power plant is a highly stressed member and 'in thickness may need to be 14 inches (35 cm.) or more and the thickness of the wall of the housing of the headers may be of the order of 8 inches ('20 cm.). Such tube plates and housings are expensive to make and the joining of the housing to the tube plates present difficul-ties in that it is difiicult to form a satisfactory bolted or welded joint between the two. In addition an opening must be provided in the housing. to permit access to the tubes and a cover plate must be bolted over said opening. The cover joint must also withstand the forces due to the feedwater pressure.

High pressure feed heaters are known in which the use of a flat tube plate is avoided by having spherical or cylindrical headers to which the tubes are joined. Such heaters often require complex tube arrangements and the headers are expensive to make. In addition difficulties often arise in welding to tubes to curved surfaces of the headers.

The object of the present invention is to provide a tubular heat exchanger which is particularly suitable for use as a boiler feedwater heater but in which tube plate and header ararngements are simplified and many of the above difiiculties overcome or substantially removed.

The invention consists in a tubular heat exchanger comprising tubes located in a casing and joined at their ends to a support member which has ducts formed therein extending transversely with respect to the tube ends, each duct communicating with one or more of the said tubes to convey fluid through the member to or from said tubes.

The invention also consists in a tubular heat exchanger in accordance with the preceding paragraph in which the support member is of block form with two opposed end faces joined by one or more side faces, the tubes being joined to one end face and the ducts extending transversely with respect to said tube ends and opening into a side face of the support member.

The invention also consists in a tubular heat exchanger in accordance with either of the preceding two paragraphs in which the support member is in the form of a flat plate with two opposed end faces, the tubes being joined to one end face, holes being formed in said plate which are co-axial with said tubes and extend from one end face to the other, the ducts passing through said plate being disposed at right angles to said holes and opening into a side face of the plate, the ends of the holes remote from the tubes being sealed.

The invention also consists in a tubular heat exchanger in accordance with the preceding paragraph in which the ducts open into the side faces of the plate via one or more further ducts at right angles to the first mentioned ducts and communicating with one or more of said first men tioned ducts.

The invention also consists in a tubular heat exchanger in accordance with any of the preceding four paragraphs in which the inlet and outlet ends of the tubes are joined to a common support member.

The invention also consists in a tubular heat exchanger in accordance with any of the preceding five paragraphs in which the ducts are circular in cross-section.

The invention also consists in a tubular heat exchanger in accordance with any of the preceding six paragraphs in which the support member is in the form of a rectangular block.

The invention also consists in a tubular heat exchanger in accordance with any of the preceding seven paragraphs.

in a boiler feedwater heater for steam turbine plant.

The invention also consists in a tubular heat exchanger substantially as described hereinbelow with reference to the accompanying drawings in which:

FIGURE 1 is a longitudinal section through a tubular heat exchanger in accordance withone embodiment of the present invention,

FIGURE 2 is a section on line A-A of FIGURE 1;

FIGURE 3 is a section through the righthand side of support member of FIGURE 1 to an enlarged scale.

In carrying the invention into effect in the form illustrated, by way of example, and referring to FIGURE 1, a tubular heat exchanger for use as a boiler feedwater heater for steam turbine plant is shown. It consists of a casing 1 housing banks of tubes 2, only the center lines of which are shown for the sake of clarity. The tubes with inlet and outlet ends are disposed in banks in the form of a double U but other tube arrangements may be used if desired.

The inlet and outlet ends of the tubes are joined to a common support member 3. The section shown through this member is not a true section in that certain holes formed in the member and aligned with the tubes have been omitted for the sake of clarity but these are described in detail below with reference to FIGURE 3. Steam from a turbine stage is admitted to the heater through inlet 4, flows over the tubes in a path which is controlled by bafiles 5, and finally leaves the heater as condensate through outlet 6.

Feedwater is conducted to or from the tubes 2 through ducts 7 formed in the member 3. These ducts extend transversely with respect to the tube ends and in the form shown are at right angles to the tube ends. It is not essential that they be at right angles but the form shown has open into the side of the member. In the form illustrated the support member 3 is in the form of a rectangular block with side faces 3a into which the further ducts 8 open. If desired the further ducts may be outside the member 3 and be connected to ducts 7.

The ducts 8 in the form shown run at right angles to the ducts 7 but this is not essential.

The arrangement of ducts 7 and 8 is to be seen more readily in FIGURE 2. The ducts on one side represent the inlet ducts and those on the other side the outlet ducts for feedwater. The support member thus serves the dual purpose of inlet and outlet header and tube plate.

Referring now to FIGURE 3, the tubes 2, shown in detail, are welded internally to end face 311 of the member 3. To facilitate access to the tubes for repair and checking purposes, holes 9 may be formed in the support member 3 as shown in FIGURE 3. These holes pass from end face 3b to opposite face 30 of the member 3 and are arranged co-axially with the tubes 2. The holes 9 intersect and communicate with ducts 7 and provide the means of communication between the tubes 2 and the ducts 7 for the flow of feedwater. During operation the ends of holes in the end face 30 of the member 3, are sealed off by means of plugs 10.

Heaters of the form described have the advantage that the member 3 combines the function of header and tube plate and whilst its thickness may be of the same order or even a little greater than conventional tube plates it is not a highly stressed member. The fluid pressure is taken up by the walls forming the ducts 7 which are preferably circular in cross-section. The need for an expensive forging to form a header is eliminated. The member 3 may be in the form of a flat plate as shown and as a result the conventional simple U-shaped or double U- shaped arrangements can be used. Access to the tube joints can be readily obtained by the simple expedient of drilling holes 9. It is also possible to carry out the internal welding of the tubes to the member 3 through these holes. The need for a high pressure joint for an inspection cover plate is also eliminated as the cover plate is no longer required.

The ducts 7 may be drilled or bored from the sides of the member 3 in which case their ends need to be plugged.

The member 3 may be cast or forged or fabricated or be a combination of any of these. Its shape need not be that shown. It may, for example, be a flat plate of circular or polygonal cross-section. It need not necessarily be of plate or block form but have a spherical shape with say one flat surface to which the tubes are joined,

Whilst the invention has been described with particular reference to its application as a boiler feedwater heater for steam turbine plant, its use is not limited thereto I claim:

1. A boiler feed-water heater comprising a casing, tubes located within said casing, the axes of said tubes extending for the greater part of the length of the tubes in directions at least substantially parallel to the longitudinal axis of the casing, said tubes having inlet and outlet ends, a fiat tube plate at one end of the casing, said tube plate having opposed end faces disposed transversely with respect to the longitudinal axis of the casing, both inlet ends and outlet ends of the tubes being joined to one end face of the tube plate, said tube plate having holes therein arranged co-axial with the tubes and extending from said one end face to the opposite end face of the tube plate, some of said holes communicating with the inlet ends of the tubes while the remainder of said holes communicate with the outlet ends of the tubes, sealing means in the ends of the holes opening into the said opposite end face of the tube plate, said tube plate having ducts therein extending transversely of and communicating with said holes, some of said ducts communicating with holes that are co-axial with the inlet ends of the tubes and the remainder of said ducts communicating with holes that are co-axial with the outlet ends of the tubes, inlet means for feed-water communicating with ducts connected to the inlet ends of the tubes, outlet means for feed-water communicating with ducts connected to the outlet ends of the tubes, inlet means for steam communicating with said casing remote fromsaid tube plate and outlet means for condensed steam communicating with said casing at the end thereof adjacent said tube plate.

2. A boiler feed-water heater as claimed in claim 1 in which the inlet means and the outlet means each comprise at least one further duct extending at right angles to the first-mentioned ducts and communicating therewith and said further ducts opening into the side faces of the tube plate.

3. A boiler feed-water heater as claimed in claim 1 in which said tube plate is constituted by a rectangular block.

References Cited by the Examiner UNITED STATES PATENTS 2,680,632 5/1954 Spieth 174 X 2,978,225 4/1961 Dallas 165-176 X FOREIGN PATENTS 114,624 1/ 1942 Australia. 763,647 12/ 6 Great Britain.

ROBERT A. OLEARY, Primary Examiner.

M. A. ANTONAKAS, Assistant Examiner. 

1. A BOILER FEED WATER HEATER COMPRISING A CASING, TUBES LOCATED WITHIN SAID CASING, THE AXES OF SAID TUBES EXTENDING FOR THE GREATER PART OF THE LENGTH OF THE TUBES IN DIRECTIONS AT LEAST SUBSTANTIALLY PARALLEL TO THE LONGITUDINAL AXIS OF THE CASING, SAID TUBES HAVING INLET AND OUTLET ENDS, A FLAT TUBE PLATE AT ONE END OF THE CASING, SAID TUBE PLATE HAVING OPPOSED END FACES DISPOSED TRANSVERSELY WITH RESPECT TO THE LONGITUDINAL AXIS OF THE CASING, BOTH INLET ENDS AND OUTLET ENDS OF THE TUBES BEING JOINED TO ONE END FACE OF THE TUBE PLATE, SAID TUBE PLATE HAVING HOLES THEREIN ARRANGED CO-AXIAL WITH THE TUBES AND EXTENDING FROM SAID ONE END FACE TO THE OPPOSITE END FACE THE TUBE PLATE, SOME OF SAID HOLES COMMUNICATING WIFE THE INLET ENDS OF THE TUBES WHILE THE REMAINDER OF SAID HOLES COMMUNICATE WITH THE OUTLET ENDS OF THE TUBE SEALING MEANS IN THE ENDS OF THE HOLES OPENING INTO THE SAID OPPOSITE END FACE OF THE TUBE PLATE, SAID TUBE PLACE HAVING DUCTS THEREIN EXTENDING TRANSVERSELY OF AND COMMUNICATING WITH SAID HOLES, SOME OF SAID DUCTS COMMUNICATING WITH HOLES THAT ARE CO-AXIAL WITH T HE INLET ENDS 